<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf8" />
	<title>Selects</title>
</head>
<body>
	<form method="post" action="filtros.php" name="select">
		<select name="select1">
			<option value="">Nada</option>
			<option value="4º ESO">4º ESO</option>
			<option value="3º ESO">3º ESO</option>
			<option value="2º ESO">2º ESO</option>
		<select>
		<select name="select2">
			<option value="">Nada</option>
			<option value="Mates">Mates</option>
			<option value="Quimica">Quimica</option>
			<option value="Historia">Historia</option>
		<select>
		<select name="select3">
			<option value="">Nada</option>
			<option value="Juanito">Juanito</option>
			<option value="Pepitp">Pepitp</option>
			<option value="Jaimito">Jaimito</option>
		<select>
		<input type="submit" value=">>" />
	</form>
</body>
<html>